Symptoms
When installing the K2 blackpearl app from the SharePoint app store into your app catalog in SharePoint online. Then you try to configure the app via registration wizard, upon the OAUTH Resource is set up we run into the error:
“Object Reference not set to an instance of an object.”
In the K2 Hostserver error log you can see the following related error:
20:10:52","Error","General","0","ErrorMessage","IntegrationService.Execute","0 System.NullReferenceException: Object reference not set to an instance of an object.
Diagnoses
Check to see if an OAuth exists within the following tables:
OAuthAppOnlyToken
OAuthResource
OAuthResourceParameter
OAuthResourceType
OAuthResourceValue
If there are no entries here it would mean the OAuth Resource token has not be created.
Resolution
A workaround would be to have a look at the Sourcecode.smartobjects.services.sharepoint.intergration.dll.config, to see if the correct mappings are in place, the best thing to do would be to get hold of an on-prem version of this config file and compare the two versions.
After this has been mapped out correctly then you should be able to get past the step within the registration wizard.
This should be done with a support engineer. So please log a support ticket if you run into this issue.